Abstract:
An artificial substrate experiment was designed to mimic the colonisation of new areas of sediment that are introduced to Lake Hoare by episodic and localised slippage of accumulations of sediment through the ice cover. These appear on the lake floor as sediment mounds. At the Lake Hoare, experimental sediments were introduced as pre-prepared frozen "sediment burgers". The burgers were placed on ... the lake floor and gradually melted leaving a uniform layer of sediment. To determine the mechanisms whereby recolonisation occurs, a series of treatments was applied including different pre-treatments of sediment (sterilisation, ashing, no treatment), thicknesses of burgers (0.3 and 2cm) and use of perspex barriers to prevent migration from below (a round plate below the burger) and from the sides (a tube enclosing the burger). The "burger menu" was: 1) Control area (no burger), 2) 0.3 cm sediment, no barrier, 3) 2cm sediment, no barrier, 4) 2cm sediment, vertical migration barrier, 5) 2cm sediment, horizontal migration barrier, 6) 2cm sediment horizontal and vertical barrier, 7) 2cm sediment, horizontal and vertical barrier, sterilised sediment, 8) 2cm sediment, horizontal and vertical barrier, ashed sediment. Each treatment was replicated 3 or 5 times. The experiment was left in situ for 4 years. Samples were collected for analysis of carbon, nitrogen, chlorophyll-a and species composition. In general the treatements showed very similar rates of colonisation, with the exception that mounds with no horizontal barriers showed the most rapid colonisation.